Micronesica 30(2):389-415, 1997 Agricultural Crop Production on Guam during the 20th Century M. MARUTANI, J. BROWN, F. CRUZ AND G. WALL College of Agriculture and Life Science , University of Guam Mangi/ao, Guam 96923 Abstract-Agriculture on Guam has changed dramatically during the pe­ riod of American governance (1898 to 1941 and 1944 to present). The pri­ mary event affecting agriculture during this period was the transition to a cash based economy. Employment for monetary wages became wide­ spread during the last years of World War II (WWII) and during the mili­ tary build-up immediately afterwards. Prior to WWII, the economy of Guam was based on subsistence agriculture . In a historic sense, the crops on Guam can be divided into three categories: (1) those that have basi­ cally disappeared as commercial commodities because of complete re­ placement by imports, i.e. rice, arrowroot, sugarcane, field corn and to­ bacco; (2) those that were important before the introduction of the cash economy and have remained relatively important for cultural or economic reasons, i.e., coconut, taro, yam, sweet potato, banana, pineapple and pa­ paya; and (3) those that have become important since the late 1950s, i.e. watermelon, cucumber, beans, eggplant, tomato and cantaloupe. In­ creased demand and erratic local supplies of fresh vegetables and fruits encourage the importation of many commodities. Sources of variation in local production of fruits and vegetables are: periodic typhoons and trop­ ical storms; soil saturation during rainy season; physiological disorders due to high temperature, high relative humidity, water stress, imbalances of soil nutrients, and the occurrence of diseases and pests. The recent emergence of landscaping and ornamental markets as well as turf man­ agement business of golf courses has diversified the island's agriculture. Some issues on Guam's future agriculture addressed are development of environmentally sound and sustainable cropping systems, new crop de­ velopment, mechanization, improvement of post harvest technology, de­ velopment of profitable market system, and further expansion of the newly developed ornamental, landscape and turf industry. Introduction More than 90% of the food consumed on Guam is imported (Economic Re­ search Center, Department of Commerce 1984) and current agricultural employ­ ment is 0.5% of total employment (Department of Labor 1995). This situation has not substantially changed in the last 25 years (Lee 1971) . Despite a steady increase 390 Micronesica 30(2), 1997 in island population since World War II (WWII) (Figure 1 ), the numbers of com­ mercial farms and growers have remained the same or decreased. The majority of fruits and vegetables consumed on the island are imported from the mainland United States, and foreign sources include Australia, Federated States of Microne­ sia, Korea, Japan, the Commonwealth of Northern Mariana Islands, New Zealand, Taiwan, Palau, Philippines, People's Republic of China, and Thailand (Department of Agriculture, Plant Protection & Quarantine 1996). There are many environmental problems that limit local agricultural production. Guam is a tropical island that receives abundant heat and light the year-round and seasonal rainfall. The island environment is characterized by occurrences of unpre­ dictable heavy rain and wind, and poor soils in most areas of the island. The periodic occurrences of typhoons constrain development of perennial crops. In addition, the introduction of new pests and diseases have created problems with crop production. Local producers frequently fail to provide a constant supply to the market due to abi­ otic and biotic constraints which results in a heavy reliance on imported produce. Social, economic, and political factors also limit agriculture on the island. A historical review of agricultural production systems on Guam reveals that the change in the socio-economic structure on the island during and after WWII has greatly in­ fluenced production patterns. Prior to WWII, the economy of Guam was primarily based on subsistence agriculture. Shifts in the labor force from farming to a wage­ based economy reduced local crop production and allowed for expanded imports of produce. Moreover, government policy on land use has greatly restricted farming ac­ tivities. Lands in the central region of the island, which were primarily in agriculture, have been expropriated for development of military bases and as business districts. This paper discusses the environmental and economic factors that have shaped the pattern of crop production on the island, focusing on historical events and the current status of agriculture on Guam. 250000 4000 --0- Population :; Agriculture Employment 200000 -+- "'E ::, :; 3000 .5. "'E C ::, 150000 - E• .s. > 2000 0 C a. .5! E ii 100000 w :i... 0 • 1000 ... ~ 50000 :i ~ <"' 0 0 1900 1920 1940 1960 1980 2000 YEAR Figure 1. Population of Guam from 1901 to 1990 and the number off arm- ers and farm laborers from 1920 to 1996. Marutani et al: Agriculture on Guam during the 20th Century 391 Environment and Agriculture GEOGRAPHY Guam is a tropical island of the Western Pacific, located at 144°55' E longi­ tude and 13°33' N latitude. The island is 48 km long and 6 to 9 km wide with a total area of 549 km 2 or 135,680 acres (Young 1988). It is the largest and the south­ ernmost island in the Mariana Islands chain, located about 6,100 km west south­ west of Hawaii, 2,600 km east of the Philippines, and about 2,500 km south south­ east of Japan. The island topography divides Guam into three major geophysical regions. The northern part of the island is a flat limestone plateau with elevations between 30 and 17 4 m. In contrast, the southern part of the island consists of mountainous uplands of volcanic origin, with a highest elevation of 407 m. Surrounding hills are divided by numerous rivers and many steep slopes which are subject to ero­ sion. Limestone is found along the south east coast and at areas around the highest point in the south. The central part of the island consists of both hilly limestone and plateaus. Development is the greatest in this area, where most government and business activities take place. SOILS A total of 55 soil types are characterized on Guam (Young 1988). These soil types are grouped together into three classes; soils on bottom lands (4%), soils on volcanic uplands (35%) and soils on limestone uplands (61 %). The soils in the first class are deep, level, poorly drained clay soils on bottoms of valleys and coastal plains. Floods are frequent during the rainy season. Soils on volcanic uplands are found in the southern parts of the island. There is a wide range of soil depths and drainage, and in general, steep slopes limit cultivation. The southern soils of vol­ canic origin have pH generally less than 5.5 (Demeterio et al. 1986a). The third class of soils overlying limestone in the northern and southeastern part of Guam are shallow and have a pH of 7 .0 or higher. Guam soils are low in phosphorus and can be limiting for crop production, es­ pecially in acid soils (Demeterio et al. 1986b). Liming to increase pH and to im­ prove availability of soil nutrients and microbial activity is a recommended prac­ tice for acid soils. In calcareous soils from central and northern parts of the island, iron and other micro-nutrient deficiencies are common due to high soil pH. Water stress is common in shallow soils overlying the limestone during the dry season and transition periods between dry and wet seasons. Many vegetable crops have been grown in the different soil regimes on Guam. Watermelon 1 which is the most important crop in economic terms and an acid-tol­ erant plant, is commonly grown in the deep soils of the southern part of the island, while many growers in the north cultivate yard-long bean and cucumber. These plants can be grown throughout the year in the field with well drained soils in the north. In general, inorganic chemical fertilizers are commonly used to supplement mineral nutrients of soils. 1Latin names of crops are given in Tables 3-5. 392 Micronesica 30(2), 1997 DAYLENGTH AND LIGHT INTENSITY Guam has daylength ranging from 11 hours and 19 minutes in December to 12 hours and 56 minutes in June. Although the difference in seasonal daylength is small, some plants display photoperiodic responses in their development. As an example, Euphorbia cyathophora L., an introduced weed from the New World, :flowersfrom December to February and winged beans flower and produce fruits from January through March. Some cultivars of potato e.g. 'Kennebec,' initiate formation of :flowers and new tubers much earlier on Guam than when they are grown in temperate regions (Marutani 1986). Early tuberization can be attributed to physiological responses to short-day conditions of Guam. Conversely, supple­ mental lighting applied to kangkong, a leafy vegetable, increases its yield by pro­ moting vegetative growth. The highest monthly average of possible sunshine (57%) was recorded in March and April, and the lowest monthly average of possible sunshine (34%) was reported in August (NOAA, 1994). The average daily solar radiation at Barrigada (centralGuam)fromJanuary 1 to March 31, 1986wasrecordedas 18.2MJ·day- 1, ranging 10.0 to 25.2 MJ·day- 1 (Marutani 1986). Effects oflight intensity on plant phenology was studied on dendrobium orchids (McConnell 1988). Dendrobiums growing in 30% shade have been found to initiate :flowering about one month ear­ lier than those grown in full sun. Vegetable seedlings which are grown in shade and are not acclimatized before transplanting to the field are usually scorched by sunlight. PRECIPITATION Average annual rainfall from 1965-1994 was 256.7 cm (NOAA 1994). Aver­ age monthly rainfall ranges from 10.4 cm (March) to 38.1 cm (August).